Lens-protractor.



I. HAMILTON.

; LENS PROTBAGTOR.

APPLICATION FILED APR. 18. 1908. V 901,61 2. Patented Oct. 20, 1908,;

, 513.4. WITNESSES. INVENTDR. WcWf M64. $m

ATTEI NEY.

I 1 TED STATES.

PATENT "OFFICE.

llREDERIGK HAMILTON. or PROVIDENCE, RHODE ISLAND, ASSIGNOR OF ONE-HALF'ro FREDERICK A. STEVENS, or PROVIDENCE, RHODE ISLAND.

LENS PRO'IRACTOR.

are. 901,312.

Specification of Letters Patent.

Patented Oct. 20, 1 908.

Application filed April, 18, 1908. Serial No. 427,793.

To all whom it may concern:

Be it. known that I, FREDERICK HAMILTON, a citizen of the United States,residing at Providence, in the county of Providence and State'of-RhodeIsland, have invented certain new and useful Improvements in Lens-Protractors, of which the followingis a specification.

My invention relates to protractors adapt ed for use in de'centermg,marking and testing lenses; andhas for its essential object;

means for guiding the operator in securing uniform positioning of thelens with relation means for elevating the graduated surface;

. means for protecting the latter'from. chips or grit; and means forincreasing, the strength, durah ht and convenience of'the structure;

. as well means for facilitating the accurate measuring of tlic lens.

' To the above ends my invention consists essentially in the novel form,arrangement,

construction, andcombination of parts hereinafter described, andillustrated inthe accompanyingdrawings, wherein, Figure l is a plan viewof my novel pro- Fig; 2, an end elevation of the same. Fig. 3,-a sectionon line a; a: of Fig.1, and Fig. 4, a bottom plan view of the same. Likecharacters of reference indicate like parts throughout the views.

My novel device comprises a plate of sheet metal, A, elliptical or ovalin outline and;

having-a curved rounded or convex body ortion, a, and a downwardly andinwardly inclined marginal flange, a. The outer sur face of the plate,A, is covered by a sheet of celluloid'or other similar material, B,which overla s the flange, a, and ,whose margin, I), is fold ed againstthe inner surface of the flange. A metallicretaining ring, C, of thinmetal is provided, angular in cross section, having a substantiallyhorizontal base portion, 0, and an upwardly and outwardl inclined sideportion, 0. The outline o the.

ring corresponds in shape with the margin of the plate, A, but is ofslightly less diameter to accommodate the folded portion, 1), of thesheet, B, between the outer surfaces of the ortion, c, vand the flange,a, by which suraces the fold, b, is frictionally retained in .fixedosition. Frictionally retamed inn r a p t e Fo unesnd c 2. 1s a Printedupon the upper surface of my device are the lens measuring graduations,E, showing in full lines, 0, the even degrees, and in broken lines, e",the odd degrees whereby the lines are unusually emphasized. In orderthat my device may perform the functions of a measure for decenteringlenses besides its functions as a mere protractor there are providedalong the major and minor axes respectively, of the scale, E, lines ofdots, F and ,G, constituting a millimeter scale.

It will. be. observed that the elliptical form of my protractorfacilitates the use of the thumb and finger to simultaneously engage theupper and lower margin of the protractor and of the lens which is beingapplied thereto. The smooth curved upper surface insures the absence ofdust or grit and is in shape particularly adapted to accommodate a lens.

I The elevation of the scale above the base enables it to bereadily'gras ed'from the bench by the operator. The s ape of the deviceenables the operator to avoid the common error of cutting a cylindricallens at a wrong axis.

.The assemblage of the parts of my structure is simple and inexpensivein practice.

In use it is only necessary to determine the amount of the power oi thelens in the direction that it is wished to decenter and after havingfirst marked the true center of the lens, it is laid on the protractor,moved extreme edges of the lens on the horizontal or- 1 O meridian ofthe protractor. When arrang ing on the cuttin machine place the lens sothe three dots represent the horizontal or 180 meridiamhavin the centralone exactly" in .the center'of the ens when out.

What Ifclaim is; .1 1. A convex lens protractor having a substantiallyelliptical outline, and provided upon its facewith graduations;

2.. A lens iprotract'oi having a substantially .elli tical outline andprovided u on its. face'j h radialgraduations and with inesofi'dotsindicating millimeters arranged along its maby the jor and minoraxes.

:5. In a lens protractor, the combination with a convex ellipticalplate, of a smooth material upon the exterior of the plate pro-' videdwith graduations, andrfneans for supporting the plate.

4. In a lens protractor, the: combination With a convex ellipticalplate, of a flange upon the margin of the plate, a smooth material uponthe plate Whosemargin is folded against the face of the flange, aretaining ring frictionally engaging the marginal fold, and a bodystrilp supported by the ring.

5. In a ens protractor, the combination with an elliptical plate, of aflange upon the margin of the plate, a smooth material upon the plateprovided with'a scale'and' whose margin is folded against the face ofthe flange, a retaining ring engaging the marginal fold,

' and a body strip mounted in the ring..

- 6. In a lens protractor, the combination with a convex ellipticalplate provided with a downwardly extending marginal flange, of a sheetofsmooth material provided with a graduated scale covering the plate andfolded against the inner face of the flange, a ring provided with ahorizontal portion and with a vertical portion, which vertical portionrests against the folded portion or" the sheet,

and a body strip resting upon the horizontal.

portion of the ring.

' 7.. A lens protractor comprising a plate of elli tic-al form withrounded body portion :an downwardly and inwardly inclined marglnalflange, ,a base, a retaining ring engaging FREDERICK HAMILTON.

Witnesses:

HORATIO E. BELLOWS, Josnrn BURNS.

